I think Steven - and the others - have always been very open and honest about the future of the series. All of them say the same thing - they love it, they would like to do more, but scheduling is incredibly difficult. It's not only Ben, there is also Martin who is just as busy. And, of course, Moftiss themselves, the crew and the other actors.
I remember Monthy Pyton said the same for years. Everybody kept nagging them to do a reunion, and they said that scheduling made it impossible.
So by saying that it might happen, but if so it's a long time in the future, they are being as open and honest as they can, I think.